Progressive cavity pump systems used for pumping liquids, such as crude oil, from wells generally have a drive head above ground with a motor that drives a polish rod. The polish rod extends downwardly through a stuffing box at the top of the well casing and connects with the top of a sucker rod that drives the progressive cavity pump at the bottom of the well.
The sucker rod can extend downwardly several thousand feet. During operation of the pump, the sucker rod twists in response to the torque applied by the motor. The sucker rod can have several hundred revolutions of twist. When the motor is shut down or loses power, the torsional energy in the sucker rod can backspin the polish rod and motor at a high speed, potentially causing damage to the drive head and motor, and injuring personnel.
Several prior known devices controlled the rate of backspin while releasing the torsional energy stored in the sucker rod. These devices include hydraulic or viscous brakes, and mechanical brakes actuated by hydraulic or centrifugal force. Generally these devices are relatively complex. These devices release the torsional energy and the twist in the sucker rod, so that when the motor is restarted, the motor rotates the polish rod several hundred revolutions before the pump starts to pump again, wasting time and energy.